Just before an earthquake hit the Greek city of Helike in 373 B.C.E., a Roman writer recorded animals acting strangely. In his journal, he recounted hordes of mice, birds, snakes and insects fleeing weeks and days in advance of the earthquake that eventually occurred.
Similar events have been tracked throughout history, including snakes that awoke from hibernation to leave China's Liaoning province just before an earthquake struck in 1975. And, as recently as 2010, animals in the Smithsonian's National Zoological Park in Washington, D.C., drastically changed their behavior in the moments leading up to an earthquake. Snakes slithered into the open, apes crawled to the tops of trees, flamingos crowded together and worried animal calls erupted from across the zoo, all seeming to act as a signal that the ground was about to shake.
But how did the animals know something was about to happen? Physicists have found that rocks release high levels of ozone gas when crushed under pressure, a finding that could eventually explain why animals seem to be able to anticipate when the earth will move. It's possible animals are able to detect a rise in ozone right before an earthquake or landslide [source: Lallanilla].
While this hypothesis could explain why so many animals act strangely behavior ahead of a temblor, scientists have yet to stumble upon a tried-and-true way to predict when an earthquake will occur. In fact, they're still searching for a way to issue an alert in advance of a quake. What if it were possible to predict a ground-shaking with a week's worth of warnings, similar to the hurricane safety information that's released days before the storm actually makes landfall? Turns out, there may be a way, and the answer could have been right under scientists' feet all along: rocks.
Using rocks to predict earthquakes could enable scientists to recognize when an earthquake is imminent up to two weeks before it strikes. Certain types of rocks are believed to act as semiconductors in high-pressure, high-temperature situations. Igneous rock, which is formed through the cooling and hardening of magma or lava, has the ability to throw off a magnetic shield when stressed. And the greater the stress, the greater the electromagnetic pulse.
Scientists at San Jose State University have been able to use this phenomenon to predict when an earthquake may occur; their predictions matched actual data collected from the electromagnetic pulses put off by rocks in advance of a real earthquake. In the future, this could lead to the installation of a series of stations along fault lines designed to "listen" for and track magnetic pulses for marked increases that could signal an earthquake. If this proposed detection method works, it could offer scientists the ability to raise the alarm weeks in advance [sources: Scoville, Lovett]..
However, detractors worry about reliability. It's not yet known whether these rocks produce electromagnetic pulses for other, less life-threatening reasons. If the rocks do send off electromagnetic pulses that don't signal an earthquake, and if a false alarm occurs, it could mean a far less reliable warning system than previously hoped for [sources: Scoville, Lovett].